1. Statement of the Technical Field
The present invention relates generally to Electronic Article Surveillance (“EAS”) detection systems. More particularly, the present invention relates to implementing systems and methods for intra-zone detection.
2. Description of the Related Art
EAS detection systems generally comprise an interrogation antenna for transmitting an electromagnetic signal into an interrogation zone, markers which respond in some known electromagnetic manner to the interrogation signal, an antenna for detecting the response of the marker, a signal analyzer for evaluating the signals produced by the detection antenna, and an alarm which indicates the presence of a marker in the interrogation zone. The alarm can then be the basis for initiating one or more appropriate responses depending upon the nature of the facility. Typically, the interrogation zone is in the vicinity of an exit from a facility such as a retail store, and the markers can be attached to articles such as items of merchandise or inventory.
One type of EAS detection system utilizes AcoustoMagnetic (“AM”) markers. The general operation of an AM EAS detection system is described in U.S. Pat. Nos. 4,510,489 and 4,510,490, the disclosure of which is herein incorporated by reference. The detection of markers in an AM EAS detection system by pedestals placed at an exit has always been specifically focused on detecting markers only within the spacing of the pedestals. However, the interrogation field generated by the pedestals may extend beyond the intended detection zone. For example, a first pedestal will generally include a main antenna field directed toward a detection zone located between the first pedestal and a second pedestal. When an exciter signal is applied at the first pedestal it will generate an electro-magnetic field of sufficient intensity so as to excite markers within the detection zone. Similarly, the second pedestal will generally include an antenna having a main antenna field directed toward the detection zone (and toward the first pedestal). An exciter signal applied at the second pedestal will also generate an electromagnetic field with sufficient intensity so as to excite markers within the detection zone. When a marker tag is excited in the detection zone, it will generate an electromagnetic signal which can usually be detected by receiving the signal at the antennas associated with the first and second pedestal.
The AM EAS detection system also comprises people counters to identify which zone a person is walking through, where a zone is defined as the space between two pedestals. This information is then used to alarm only those zones that have both an AM marker and a person present therein. The AM EAS system can use AM marker amplitude to estimate which pedestal the AM marker is closest to, but multiple pedestals or multiple marker sources reduce efficiency and cannot determine which side of the pedestal a marker signal is coming from. The addition of people counters defines the specific zone further by excluding other zones a pedestal covers if there are no people present.